1. Technical Field
The present disclosure relates to a communications system that enables a plurality of sites, each including a plurality of terminals, to communicate with each other.
2. Description of the Related Art
Recently, video calling services that allow the user(s) of at least one video call terminal at one site to talk with the user(S) of at least one more video call terminal at a distant site have become more and more popular. According to these services, however, it is not that one video call terminal at one site and another video call terminal at another distant site are simply directly connected together, but communications are carried out between those sites via a plurality of routers that each of those sites has.
For example, services that allow a passenger using a video call terminal at a seat of an airplane to have a video talk with someone using a video call terminal on the ground via a plurality of routers, a plurality of antennas installed on the airplane and on the ground, and a communications satellite have just started to be provided.
In such inter-site video calling services, only a limited bandwidth (or communications rate) is available for each site, and therefore, it is important to perform a bandwidth control according to the status of an ongoing video call. The bandwidth control is important in not only such video calling services but also any other form of service that requires to transmit data of a huge size.
Japanese Laid-Open Patent Publication No. 2005-109744 discloses an exemplary bandwidth control method. In the CATV system disclosed in FIG. 4 of Japanese Laid-Open Patent Publication No. 2005-109744, a cable modem CM can change the frequency ranges that are currently used by personal computers PC1 and PC3 connected to the modem following a predefined condition.
In one embodiment of Japanese Laid-Open Patent Publication No. 2005-109744, by setting the condition on the number of personal computers connected, if only a few persons are using those personal computers, the bandwidth available for each of them can be broadened. And even if the number of persons using the computers has increased, the bandwidth available for each of them just needs to be narrowed. Thus, optimum bandwidth setting can be made according to the number of personal computers connected.